192 GEOLOGICAL SURVEY OF THE TERRITORIES. 



The subject of irrigation is one inseparably connected with the agri- 

 cultural development of this section, and deserves to be carefully stud- 

 ied. The time given for the preparation of this preliminary report has 

 been too short to enter upon a thorough discussion of it, but I have 

 added a few facts in my concluding remarks, in order to direct atten- 

 tion to the data needed in its investigation. 



If you continue your surveys I would suggest the propriety of filling 

 up as rapidly as possible the vacuities in the data obtained in regard to 

 the sections already passed over. I am aware that you did not possess 

 the facilities for doing this in your previous expeditions, but the value of 

 your previous labors, so far as the agricultural investigations go, will be 

 very much enhanced by doing this. I allude to the measurement of the 

 principal streams, their descent, volume, velocity, &c, and the compar- 

 ative altitude of the different levels and plains above the level of the 

 irrigating streams, by some instrument more accurate than the ba- 

 rometer. 



I take pleasure in acknowledging my obligations to the citizens gen- 

 erally along our route, for information obtained from them, and espe- 

 cially to the officers and others at the military posts, for their uniform 

 kindness and willingness to assist me in my investigations. I am also 

 under obligations to the Denver Pacific and the Kansas Pacific Bail- 

 roads, for passes over these roads and information furnished. Nor can 

 I refrain from mentioning the fact that I am indebted to Win. N. Byers, 

 esq., of Denver, and Dr. Latham, of Laramie City, for valuable ma- 

 terial furnished me for this report. 



I am aware this report bears marks of haste, and that it is far from 

 being complete, but trusting that it will prove satisfactory, 

 I remain yours, very respectfully, 



OYBUS THOMAS. 



Professor F. Y. Hayden, 



United States Geologist. 



PABT I.— AGBICULTUEE. 



INTRODUCTION. 



In studying the agricultural capacity of the vast Eocky Mountain 

 region and broad plains of the West, and calculating the probable 

 development of the same, it is necessary to lay aside, to a great extent, 

 all our ideas of agriculture based upon experience in the States. For 

 not only are the physical aspects of this portion of the West so different 

 from the eastern half of our country as to strike the most superficial 

 observer, but the climate is almost completely reversed, the thermom- 

 etric and hygrometric conditions bearing no such relations to vegetation 

 and agriculture here as there. 



Hence, the criteria by which we judge of the fertility and productive- 

 ness of the soil, and of its adaptation to given products, (except, perhaps, 

 the strictly chemical test,) do not hold good here. The pale appearance 

 of the soil, the barren look and stunted growth of a spot, are by no means 

 conclusive evidences of its sterility, for the application of water may 

 show it to be rich in vegetative force. Plants which are considered as 

 incompatible in other sections are often here found growing side by 

 side, while others usually associated are here never, or but seldom, found 

 together. Even the constants — latitude and elevation — cannot always 



